SEATTLE — No cashiers, no lines, no registers — this is how Amazon sees the future of in-store shopping.

The online retailer opened its Amazon Go concept store to the public Monday, selling milk, potato chips and other items typically found at a convenience shop. Amazon employees have been testing the store, which is at the bottom floor of the company’s Seattle headquarters, for about a year.

The public opening is another sign that Amazon is serious about expanding its physical presence. It has opened more than a dozen bookstores, taken over space in some Kohl’s department stores and bought Whole Foods last year, giving it 470 grocery stores.

But Amazon Go is unlike its other stores. Shoppers enter by scanning the Amazon Go smartphone app at a turnstile. When they pull an item of the shelf, it’s added to their virtual cart. If the item is placed back on the shelf, it is removed from the virtual cart. Shoppers are charged when they leave the store.

The company says it uses computer vision, machine learning algorithms and sensors to figure out what people are grabbing off its store shelves.

Amazon says families can shop together with just one phone scanning everyone in. Anything they grab from the shelf will also be added to the tab of the person who signed them in. But don’t help out strangers: Amazon warns that grabbing an item from the shelf for someone else means you’ll be charged for it.

At about 1,800 square feet, the store will also sell ready-to-eat breakfasts, lunches and dinners. Items from the Whole Foods 365 brand are also stocked, such as cookies, popcorn and dried fruit.

The company had announced the Amazon Go store in December 2016 and said it would open by early 2017, but it delayed the debut while it worked on the technology and company employees tested it out.